Method of operating flaming-arc lights for projectors.



E. A. SPERHY.

METHOD 0F OPERATING FLANIING AHC LIGHTS FOR PROJECTORS. APPLICATION FILED JUNI: 28. 1915.

1,227,2 l O. Patented May 22, 1917.

MM 5I, im

ELMER A. srnnnY, or BROOKLYN, NEW YORK.

METHOD 0F OPERATING FLAMING-ARC LIGHTS FOR PROJECTOBS.

Specification of Letters Patent.

Application led June 28, 1915. Serial No. 36,615.

To all whom 'it may concern ,Be it known that I, ELMER A.. SPERRY, a citizen of the United States of America, residing at 100' Marlborough road, Brooklyn, New York, have invented certain new and useful Improvements in Methods of Operating Flaming-Arc Lights for Projectors, of which the following is a specification.

The object of this invention is to provide a source of light for search lights, projectors and the like which will emit a higher candlepower per unit area of light source than can be obtained from the ordinary carbon arc.

In order to accomplish this I employ a direct current arc of a different sort and possessing very different qualities from the direct current arcs ordinarily used.

As is well known, the light emitted from the positive crater of a carbon arc possesses the highest intrinsic brilliancy or candlepower per unit area of any incandescent light source, and this source has therefore remained the standard search light source since the earliest days of the art.

The arc I employ not only utilizes to its best advantage the light from the incandescent electrode tip, but in addition to this a volume of luminescent or brilliantly glowing vapor of much higher temperature than the electrode tip is made use of. This vapor is persistently maintained and, what is of the utmost importance, is confined to such a portion of, and position in, the arc that substantially its total light emissivity isavailable as a source of light for search lights, and its light is therefore, it is believed, an additive quantity to the light of the incandescent electrode tip or crater, While at the same time the area of the light source is not materially increased as compared to a pure carbon arc employin a positive electrode of the same size. In act the light source is greatly reduced as compared to the standard pure carbon arc employing the same amperage as applicant employs. In this way the intrinsic brillianc of the available light is very greatly multiplied, being doubled or even ytrebled.

Referring to the drawings :Figure 1 represents an arc ordinarily produced where the carbon consumption is low and the positive forms a blunt rounded tip either with or without a very definite crater. Fig. 2 shows an arc operated at high current density. but uncontrolled, showing how the positive and negative dames tend to ride up on each other making a high pointed arch with considerable increase of voltage.

Fig. 3 shows somewhat improved burningA conditions, but Where the positive flame is not suiiiciently confined but has been allowed to lap out under the negative flame.

Fig. 4 shows the flames when the positive and negative are out of line laterally.

Fig. 5 shows the burning conditions where the negative carbon is tilted at such an angle that the negative iiame has not of itself suliicient force of impingemeni-J to overcome the positive pressure, allowing the positive llame to escape.v In this figure an attempt is made to take the negative tip out of the zone of useful light (indicated by dotted lines) intercepted by the mirror.

Fig. 6 shows the arc under proper conditions of operation, where a cored carbon is employed.

Fig. 7 shows the electrodes in the same relative positionl as Fig. 5 where the carbon Patented May 22, 1917. v

is well out of the zone of useful light 'Y (shown in dotted lines) but where the proper impingement is effected by an extraneous directive means or force, in this instance consisting of a solenoid placed back of the said zone and suitably energized for purposes of causing proper impingement of the negative flame with the positive.

The first essential of my invention is the operation of the electrodes with sufficiently heavy current or amperage tol produce a distinct flame issuing apparently from both the positive and negative electrodes. At present I employ from 90 to 150 amperes. It is equally important that the positive electrode be (operated at high current density, that is somewhere in the neighborhood of 500 amperes per square inch or more. The current density employed in the negative seems to be practically immaterial,

as good results have been obtained with comparativelyv low current density, but, as above stated, to obtain the phenomena characterizing my invention, I depend upon the total current flowing. But, as shown in the drawings, I prefer to use a very slender A negative 3, in order, especially for projector Work, that' a minimum shadow may be cast thereby. It frequently happens therefore, that the current density in the negative rises to more than 1,000amperes per square inch. 'Ihe negative carbon-,is preferably provided With a core 4 containing arc supporting but not necessarily light emit- -lar in appearance to that ordinarily produced (see Fig. 1). The carbon consumption is very slow and the positive forms a blunt rounded tip 5. The luminous flame 6 extends across the entire arc length from positive to negative. There is furthermore no observable separation or division between the positive and negative-flames.

When, however, the current is increased to the above mentioned extent, very'diferent phenomena make their appearance. The

tip of the positive carbon at this high current density has a strong tendency to form a deep crater 7, due to the increased rate of consumption of the positive core. The arc flame, moreover, has also changed its characteristics; it now consists of two very distinct and well-defined portions, one of which is apparently emitted from each electrode and which we will therefore call the negative flame 8 and the positive flame 9.

The success of this invention depends on the proper utilization of this negative flame in combinationI with two other essentials of this intensive arc. First, the intensely luminous positive flame, second, the deep positlve crater, whlch 1s used as the contamer for this luminous flame, the negative flame or' blast being employed to impinge against and thus confine the luminous flame substantially in its entirety to the crater.

In order to cause the nega-tive flame to accomplish these results, I have found that the negative flame should take the form of an actual' blast propelled at considerable velocity from the negative tip. This blast is such that it exerts a strong pressure against whatever it may impinge.

yAccording to my invention I so adjust the burning conditions. that the positive flame also has considerable pressure though not somuch as the negative. Its pressure is, however, not due to the speed of its particles, as apparently is the case with the negative, but is caused by the abundant supply of the vapor from the rapidly consumed positive electrode 1, especially of the core 2 thereof. A

This rapid continuous supply of the luminescent vapor from the positive causes a steady pouring forth of the positive flame 9 which considerably overflows the crater 7.

To illustrate one of the difficulties overcome in properly controlling the positive and negative arc flames it should be pointed bly eleven volumes of positive vapor volatilized for one volume of negative and notwithstanding this very great disparity in volume emitted, I have been able to control the positive flame chiefly by obtainin a higher velocity for the very much sma ler volume from the negative tip and in properly directing and keeping this negative flame steady.

In addition to giving the negative flame a high velocity, I have discovered that in order to give the arc the required stability or steadiness in service it is necessary to provide means for giving the negative flame a strong and dependable directive influence Q which will cause it to maintain with its high velocity a constant direction of blast a ainst any couner-pressure of the positive In other words, I find this arc, when of the proper length, to be inherently unsteady, even to an extent which will cause it to extinguish itself, unless some extra steadying force is given to the negative flame or blast which will prevent any deflecting pressure, such as upward air currents, once the arc is properly adjusted and directed, from changing this direction or diverting it, i..e. the negative flame as a whole.

For instance, if a solid negative carbon 3 is employed,'the requisite arc length maintained and no other extraneous means are provided for directing the negative flame, the positive and negative flames 9 and 8 tend to ride up on each other as shown in Fig. 2, making a high arch 10, and the voltage across the arc increases to time.

such an extent that the arc is very un-l steady and gmost easily extinguished. Also it is notedthat the negative flame does not issue steadily from the tip, but shows a tendency to issue from theptop as shown at 25.

I have tried various directive influences l `In order to use this directed negative blast so that it may-confine the positive flame to the best'advantage, I find it necessary to cause a definite impinging contact between the two flames across they crater mouth in such a manner that a steady and somewhat upwardly inclined current is 'created at the contact of the two flames (Figs. 3, 6, 7 This sort'vof impingement mamie still allows a steady, but not too free, escape of some of the spent positive luminous ,vapor in a constant direction and thus prevents flaring and flickering of the arc which results when the flame from the positive crater is allowed to escape in any undeter- *mined direction, as it is necessary that it remain under perfect control by the negasides the luminous gases cover a much greater volume than is desirable as a source of light for projectors. l

Fig..4 shows the two carbons out of line laterally so that one side of the positive crater is unprotected bythe impingement of the negative* iiame against the positive flame which escapes from this uncovered portion as shown.

' Fig. 6 shows the carbons running under the desired conditions, .the positive flame being entirely confined to the vicinity of the crater bythe proper impingement on.

the kpart of the negative flame and the escape of a limited amount of the positive llame being kept steady over the upper lip A of the crater.

The' positive flame is apparently partially trapped or confined substantially in its eni tirety tothe crater and curled upwardly and backwardly by the negative blast,'escaping only at the .top or in the general direction l of the negative flame. A ball 11 of more or less condensed luminous vapor is thus produced which is available as a source of light for projectors in addition to the positive crater.-

It has been proposed to so position the negative electrode' with respect to the positive in search lights that no shadow will be cast thereby. Fig. 5 shows the flame conditions that present themselves. Thenegative carbon is evidently tilted at such an angle that there is not sufficient force of impingement to overcome the positive pressure and therefore the positive flame escapes in a long flame 22 and its light is unavailable as a concentrated source. One method of overcoming this difficulty is shown in Fig.' '7. Here a coil of wire 15 or the like is arranged s'o as to deflect the two flames by its electromagnetic action and cause them to assume burning conditions 'similar to those shown in Fig. 6.

In addition tothe necessity of controlling the flames as above-stated, I find the maintenance of a deep, symmetrical positive crater to be of pr'me importance, for it is within this crater that the luminescent gases are trapped.

In order to maintain the depth and symmetry of the crater I find it desirable to rotate the positive carbon continuously which condition is represented by the arrow 20. |Ihe rotation has a double advantagef Itprimarily causes the deep crater to be permanent and symmetrical by preventing the burning away of the upper lip. But, furthermore, when the arc is operating as shown in Figs. 6 and 7 the emitted or exhausted vapor from the arc licks the outer rim of the positive crater as it turns and deposits on the outside of this rim a continuous graphite ring 23 which performs the extremely useful function of protecting the positive'carbon from excessive tapering at the outer edge of the crater or electrode tip, which being the hottest exposed portion of the positive electrode is the part for which protection is most necessary.

With reference to the voltage across the arc, Fig. 1 may be considered as representing the arc produced by a flaming arc positive, wherein the normal arc length is found to be easily maintained with even a very low amperage, say 30 to 40 amperes. This all takes place when the carbons are running at their normal current density, meaning by this a current density at which an ordinary carbon will not glow or rise in temperature to a point of rapid oxidation at any point back of the tip. The voltage under these conditions is found to be about 30.

volts.

` As compared with this voltage, the Voltage of the arc shown in Fig.'2, which it will be remembered is operated at high current density, runs up as high as 90, is easily extinguished and is unsteady.

In Fig. 3 it may not run up as high as 9() but is still unsteady.

` The arc of Fig. 4 behaves very similarly to the arc of Fig. 2.

The arc shown in Fig. 5 is somewhat lower in voltage than that of Fig. 2, owing to the shorter path of the current and possibly also to the larger contact between the flames, but is not useful as a concentrated light source, being unsteady and of too great an extent.

The arcs in Figs. 6 and 7 are, steady, reliable and very concentrated and the voltage becomes about 7 0-75 volts.

It will be noticed that where the arc flame and especially the positive llame is allowed to escape and is not suppressed or impinged, that the voltage is increased to something like 90, as has been above pointed out. This elevated voltage may be due to lengthening of the path between the electrodes.

variably producing by using negative electrodes with the core of more refractory material than the shell so that the-negative will burn to a slender point. It will be noticed that I prefer to employ carbons having just the reverse burning characteristics, inasmuch as the core is more rapidly burnin than the shell, in-

a enitel concavity or crater at the tip o the negative, which ap# parently aids in imparting a definite directive force to the negative fiame.'

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. The method of operating flaming arc lamps for projectors under conditions producing a two flame arc, which consists in confining the positive flame of such arc substantially in its entirety to the positive crater by the action of the negative flame, permitting its escape only in the direction of the negative flame.

2. The method of operating iaming arc lamps for projectors under conditions producing a two flame arc, which consists in directing the negative fiame of such arc past l the positive at such an angle as to conne the positive flame substantially in` its entirety to the positive crater, permitting its escape only in the direction of the negative flame.

3. The method of operating flaming arc lamps for projectors under conditions producing a two flame arc, which consists in rotating the positive electrode, and directing the negative iame of such arc past the positive at such an angle as to conne the positive iiame substantially in its entirety to the positive crater.

4. The method of operating aming arc lamps for projectors in which the negative electrode contains a core of more rapidly 'burning material than the shell, which consists in employing sufficient current to produce two distinct llames and directing the high velocity negative ame at such an angle to the positive electrode as to confine the positive flame substantially in its entirety to the positive crater.

5. The method of operating flaming arc electrodes of carbonaceous material for projectors, which consists in rotating the positive electrode, directing the negative iame' loying sufficient current to produce twol v istinct flames and directing the high velocity negative fiame at such an angle to the positive as to confine it substantially in its entirety to the positive crater.

7. The method of operating aming arc lamps for projectors in which the negative yelectrode contains a core of more rapidly burning material than the shell, which consists in employing sulicient current density in the positive to produce a distinct positive iame, and in employing sufficient current to produce a high velocity negative fiame to which suicient directive force is imparted by reason of the core to be substantially undeflected by the presence of the positive flame.

In testimony whereofv I have signed my name to this specification this 25th day of` June, 1915.

ELMER A. SPERRY. 

